1. Field of the Invention
This invention relates to a cord tightening device made of synthetic resin and used for tightening cords which are fitted on anoraks, rucksacks, life jackets, shopping bags, etc. for the purpose of tightening them.
2. Description of the Prior Art
As a tightening device of this kind, the rope tightening device which comprises an angularly columnar hollow body formed of a top wall and a bottom wall separated parallelly from each other and opposed lateral walls and a movable arm device disposed inside the hollow body, the movable arm device being provided with four grip parts endowed with springiness and disposed as opposed to the lateral walls of the hollow body so as to allow insertion therebetween a rope or a cord bent in the shape of a loop and press the rope or cord against the lateral walls of the body thereby tightening it, and the rope tightening device further comprising a built-in release device capable of being manually operated to relieve the grip parts of the work of exerting pressure on the rope has been known (see Japanese Patent Publication No. SHO 57-42,552).
As another cord tightening device of the kind under discussion, the cord tightening device which comprises a hollow body of a generally trapezoidal plan view and a slider, the hollow body being provided in the opposite end parts thereof with a small-width opening and a large-width opening and on a front plate thereof with a slide hole, and the slider being provided with a tightening part for tightening cord portions by pressing them against the lateral plates of the body and an operating part integral with the tightening part and protruding from the surface of the hollow body through the slide hole bored in the front plate is disclosed in Japanese Utility Model Publication No. HEI 2-46,731 and the corresponding U.S. Pat. No. 4,765,034 issued Aug. 23, 1988 to Kasai. In this cord tightening device, the slider is provided with an aperture larger than the outer boundary of the operating part, and the operating part is resiliently cantilevered to the tightening part and normally overlying the aperture. The front plate is provided on the rear surface thereof at the large-width opening side of the body with a guide groove for guiding the operating part of the slider in the direction of the slide hole of the hollow body.
Besides, the loop tie clasp which comprises a hollow body of a generally trapezoidal plan view provided at each of the opposite ends thereof with an opening so shaped as to permit insertion therethrough of a loop tie and a slider disposed in the hollow body so as to nip the opposed halves of the loop tie in cooperation with the lateral walls of the hollow body, the hollow body having a guide hole formed in the front plate of the body in a shape similar to the outer boundary of the body and a stopper piece adapted to prevent the loop portion of the tie from entering tile hollow body and disposed in the center of the large-width opening at one end part of the body between the front plate and the rear plate of the body, and the slider having an operating part projected therefrom and adapted to be inserted in the guide hole so as to protrude from the front surface through the guide hole and attain operation of the slider from the front surface of the hollow body is disclosed in Japanese Utility Model Publication No. HEI 4-44,575.
In the first case of the heretofore known cord tightening devices cited above, since the opposite lateral walls of the hollow body or the case are parallel or symmetrically arcuate, the grip parts of the movable arm device for nipping a cord in cooperation with the case nip one and the same cord at two points thereof and the gripping actions produced by the grip parts in this case are exerted in mutually opposite directions. The release device for relieving the grip parts of the work of nipping the cord is disposed at two points on each of the lateral sides so as to fulfill the function thereof at a total of four points. The movable arm device and the release device are separately formed or two movable devices are formed instead and a spring is interposed therebetween. Thus, they greatly add to the complexity of construction of the whole cord tightening device. Moreover, since the grip parts are caused by the spring to generate contradictory actions, the operation for releasing the cord does not always proceed smoothly to effect release of the cord infallibly.
Then, in the case of the second and the third example, since the operating part for governing the actions of the slider so as to nip the cord or the loop tie in cooperation with the hollow body is disposed so as to protrude from the front surface of the hollow body, the operating part has the possibility of touching some other object and, as a result, readily loosing the cord and depriving the cord tightening device of the tightening effect thereof. Further, the protrusion of the operating part from the front surface of the hollow body forms a detrimental factor from the standpoint of design.
Further, in the case of the third example, since the guide hole similar in shape to the outer boundary of the hollow body is formed in the front plate of the hollow body and, as a result, the operating part of the slider is allowed to reciprocate in both the longitudinal and the lateral direction and the slider is allowed to change position freely toward the lateral walls of the hollow body, the clasp functions satisfactorily as a cord tightening device which is not exposed to the tension of a cord such as a loop tie. In a cord tightening device which is exposed directly to a tension, however, the clasp is incapable of playing the role of a tightening device.